In the case of a crane disclosed in European patent publication 0 476 225 A2, the outer boom member and furthermore the outwardly telescoping members possess spring-loaded locking bolts on their outer end on opposite sides, spaced symmetrically with respect to the luffing (lifting) plane, such bolts fitting into holes in the members encompassed by the bolts and being able to be moved out from the locking holes against a spring force by pneumatic bolting cylinders. The bolts can be locked in the locking holes by letting off of air.
In the known crane, supply lines must be laid in the individual boom members of the telescoping boom which are able to be extended and retracted in order to be able to get compressed air to the bolting cylinders. The arrangement of supply lines in the telescoping boom is not only intricate, but furthermore renders necessary the provision of large intermediate spaces between the individual boom members or telescoping boom members so that the telescoping boom members are generally not able to correspond to the full cross section of the boom members encompassing them, and must be designed with correspondingly smaller cross sections.